Control and regulator device for a load-independent regulated hydraulic system

ABSTRACT

A control device for the control and load-independent regulation of hydraulic consumers of hydraulically driven installations, a pressure-influencing valve with a pressure reducing piston being present, said valve being in controllable flow connection with a load pressure pilot bore, there also being present a control piston for producing a constant leakage loss, said device being suitable for maintaining even a slight pressure difference, whilst upon application for the load-independent regulation of a plurality of slide members, the pump pressure will adjust itself to the highest load pressure.

United States Patent Koppen et al.

[ 1 Oct. 15, 1974 CONTROL AND REGULATOR DEVICE FOR A LOAD-INDEPENDENT REGULATED HYDRAULIC SYSTEM Inventors: Dirk Jan Koppen, Scheveningseweg 102 A, The Hague; Hendrik Theodoor Metz, Jonkerlaan l7, Appingedam, both of Netherlands Filed: Sept. 26, 1973 Appl. No.: 400,897

Related US. Application Data Continuation-impart of Ser. No. 267,206, June 28, 1972, abandoned.

Foreign Application Priority Data June 29, 1971 Netherlands 7108960 US. Cl 60/462, 60/484, 91/414 Int. Cl. FlSb 11/16 Field of Search 60/420, 431, 445, 452,

References Cited UNITED STATES PATENTS Vickcrs 60/462 2,713,772 7/1955 Horlochcr 60/452 X 2,782,598 2/1957 Gatwood 1 60/462 3,406,850 10/1968 Hancox 60/452 X FOREIGN PATENTS OR APPLICATIONS 444,601 2/1968 Switzerland Primary Examiner--Edgar W. Geoghegan Attorney, Agent, or FirmDepaoli & OBrien 1 1 ABSTRACT A control device for the control and load-independent regulation of hydraulic consumers of hydraulically driven installations, a pressure-influencing valve with a pressure reducing piston being present, said valve being in controllable flow connection with a load pressure pilot bore, there also being present a control piston for producing a constant leakage loss, said device being suitable for maintaining even a slight pressure difference, whilst upon application for the loadindependent regulation of a plurality of slide members, the pump pressure will adjust itself to the highest load pressure.

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saw 11 nr 12 I PAIENIED v, 334L096 saw 120? 12 CONTROL AND REGULATOR DEVICE FOR A LOAD-INDEPENDENT REGULATED HYDRAULIC SYSTEM CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of United States application Ser. No. 267,206 of Koppen et al. filed June 28, 1972, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a control and regulation device for the control and the load-independent regulation of hydraulic consumers of hydraulically driven installations.

2. Description of the Prior Art Swiss Patent No. 444,601 describes such a device having at least one control valve unit, each comprising two consumer ports and a control spool valve through which each consumer port can be selectively connected with a pump channel or a return channel, as well as a pressure regulating valve unit for maintaining a constant pressure difference between said pump channel and the consumer ports connected with said pump channel, said unit comprising a regulating spool valve which, as a result of the action of the pump pressure at one end thereof and the action of the consumer pressure propagated from said last mentioned consumer ports via pilot bores, as well as a regulating valve spring at its other end, forms a regulating throttle orifice between pump channel and return channel, while supply and discharge means are provided for the hydraulic medium towards and from said pressure regulating spool valve.

A drawback of this known device is that the pressure difference to be kept constant by the pressure regulating spool valve can only be influenced by exchange of the spring of this valve. In case a rather weak spring is chosen, there will be the risk that the pressure regulating spool valve, during the control functioning, is not moved with sufficient reliability. Another drawback is that when the pressure regulating spool valve is applied with more than one control valve unit, and there being for instance two control spool valves simultaneously in an operable position, the pump pressure adjusts itself to the lowest load pressure.

SUMMARY OF THE INVENTION The invention aims at avoiding the above drawbacks, in a fluid control device for influencing the pressure difference between a pump channel and consumer ports connected to said pump channel, by interrupting the pilot bores, which are to be selectively throughconnected by a main gland of the corresponding control spool valves with said consumer ports, by pressureinfluencing valve cartridges.

According to one embodiment of the invention, each of said pressure-influencing valve cartridges comprises a pressure-influencing piston which, by variation of the axial displacement, forms a pilot throttle orifice in said pilot bores, whereby one end of said pressureinfluencing piston is under the influence of the pressure upstream of the pilot-throttle orifice and its other end is under the influence of the pressure downstream of the pilot-throttle orifice and of a pressure-influencing cartridge spring. There is furthermore present a leak piston, which interrupts leak bores branching from pilot bores downstream from the pilot-throttle orifices and leading to the return channel, said leak piston forming in said leak bores a first leak throttle orifice for producing a constant leakage, whereby one end of the leak piston is in a first leak chamber and under the influence of the pressure in the pilot bores and its other end in a second leak chamber and under the influence of the pressure downstream the leak throttle passage through said leak piston but upstream of a second leak throttle orifice formed between said second leak chamber and second leak bore, as well as under the pressure of a leak piston spring.

BRIEF DESCRIPTION OF THE DRAWINGS In explanation of the invention, an embodiment according to the invention will be described with reference to the drawings, while a number of possible variants will be explained by way of some hydraulic diagrams.

In the drawings:

FIG. 1 is a side view of the device,

FIG. 2 is a front view thereof,

FIG. 3 is a top view thereof,

FIG. 4 is a cross-section on the line IV-IV in FIG.

FIG. 5 is a cross-section on theline VV in FIG. 3,

FIG. 5A is a cross-section of the pressure-influencing valve cartridge in FIG. 5, but on an enlarged scale,

FIG. 5B is a cross-section of a varient embodiment of a pressure-influencing valve cartridge,

FIG. 6 is a cross-section on the line VIVI in FIG.

FIG. 7 is a cross-section on the line VIIVII in FIG. 1, with omission of pressure-balance piston,

FIG. 8 is a cross-section on the line VIII-VIII in FIG. 1, with omission of pressure-balance piston,

FIG. 9 is a cross-section according to the line IX-IX in FIG. 7,

FIG. 10 is a cross-section on the line XX in FIG.

FIG. 11 ia cross-section on the line XI-XI in FIG. 7,

FIG. 12 is a cross-section on the line XIIXII in FIG.

FIG. 13 is a cross-section on the line XIIIXIII in FIG. 8,

FIG. 14 is a cross-section on the line XIV-XIV in FIG. 8,

FIG. 15 is a hydraulic diagram for the control device in the embodiment with load-independent 3-way volume control, in combination with a pump with a constant piston stroke,

FIG. 16 is a hydraulic diagram for a control device with load-independent 2-way volume control for application in a circuit fed by a pressure accumulator, or by a pump with a controllable pump yield, or equipped with a constant-pressure control member;

FIG. 17 is a hydraulic diagram for a control device for the load-independent control of the output of a pump with a controllable pump yield on the volume not passed by the control device; and

FIG. 18 is a hydraulic diagram for a loadindependent control device for the load-dependent reduction of the output of a pump having a controllable pump yield.

DEFINITIONS AND TERMINOLOGY Definition Nos.

FIG.

Nos.

Definitions l.3.6.7.8.9.l0 .l l. Pressure regulating valve unit for H6 7 l2. l3 and I4 l.2.3. and 6 land6 land4 land4 4and6 4and6 4and6 4and6 4and6 discharge of the pump pressure in the neutral position of the control valve unit 2. as well as for the production of a constant pressure difference required for a load-independent volume flow control.

Control valve units a. b and c for directing the hydraulic fluid to and from the consumer. and for the production of a controlling throttle opening between pump and consumer. Retaining plate for keeping together the several components by means of tie rods, as well as for interconnecting the two return channel sections 5011 and 50c to build return channel 50. Pump port of pressure regulating valve unit l.

Return port of pressure regulating valve unit 1 for discharging the return hydraulic fluid to the reservoir. Second consumer port disposed at each control valve unit 2 and communicating with pump channel 48 or with return channel section 50c. First consumer port disposed on each control valve unit 2 and connecting with pump channel 48 or with return channel section 50a.

First pressure-influencing valve cartridge screwed into a control valve unit 2 and communicating with consumer port 7.

Second pressure-influencing valve cartridge screwed into a control valve unit 2 and communicating with consumer port 6.

Control spool valve. present in each of the control valve units 2 serving for determining the effective direction of a consumer; responsible for starting. stopping and reversing consumer movements; also determines the size of the controlling throttle opening for the hydraulic fluid quantity per time unit to be passed to the consumer. Control land on spool valve 10. corresponding with consumer port 7. responsible for forming the throttle orifice between pump channel 48 and consumer port 7.

Control land on spool valve 10. corresponding with consumer port 6. responsible for forming the throttle orifice between pump channel 48 and consumer port 6.

Control land on spool valve 10. corresponding with consumer port 7 and return channel 50a.

Control land on spool valve l0 corresponding with port 6 and return channel 50c.

Definition Nos.

FIG. Nos.

Definitions 4and6 Cylindrical control valve bore wherein spool valve 10 is slidably displacablc. so that in neutral position the consumer ports 6 and 7 are shut off from pump channel 48 on the one hand and from return channel sections 50c. 50:: respectively on the other; upon displacement of spool valve l0 in the first direction. pump channel 48 is connected to consumer port 6 and consumer port 7 with return channel 500: upon displacement in the second direction pump channel 48 is connected with consumer port 7 and consumer port 6 with return channel 50c (naturally there are many variants possible here).

Pressure regulating spool valve in pressure regulating valve unit I for producing a constant pressure difference between the pump pressure in pump channel 48 and the consumer pressure; to this effect loaded at one end with the pump pressure. and at the other end by a spring. as well as the consumer pressure fed back via pilot bores from one of the consumer ports 6 or 7.

Cross bores in the interior of spool valve 16. serving for transmitting the pump pressure from pump port 4 via chamber 46 to the non-spring-loaded side of spool valve 16.

Cylindrical bore in valve unit I wherein spool valve 16 is slidably displaceable. whereby the connection. dependent of the amount of spool valve displacement. between the chamber 46 and the chamber 47 is fully interrupted or there is formed a throttle orifice therebetwecn. Regulating valve spring acting on spool valve 16 and responsible for the constant pressure difference between pump pressure and the consumer pressure feedback to spool valve 16. Pressure limiting valve serving for limiting the maximum permissible system pressure and acting on the feedback consumer pressure on pressure balance piston l6; when the pressure on this pressure limiting valve 20 exceeds the maximum set. said valve is opened and hydraulic fluid from the chamber 52 is passed to return channel 50. thus maintaining the consumer pressure feedback at a value below the maximum value set. and thus controlling also the maximum pump pressure.

Valve seat for pressure limiting valve cone 22.

Valve cone of pressure limiting valve 20; is together with valve seat 2l responsible for closing and opening the connection between chamber 52 and return channel 50.

Pressure limiting valve spring acting on pressure limiting valve cone 22; the force of said spring determines the maximum allowable system pressure. Shoulder piece for good support of spring 23.

Screw pin acting on shoulder piece 24. serving for adjusting and thereby varying the force of spring 23. Adjustment nut to be screwed and pinned on screw pin 25. for the adjustment of spring 23.

Lock nut for securing screw pin 25. Pressure-influencing piston in pressure-influencing valve cartridge 8 or 9'. responsible for producing a constant pressure drop in the consumer pressure feedback to the pressure regulating valve unit 1.

First gland of pressure-influencing piston 28. whereon the primary consumer pressure feedback is acting.

-Cont1nued -Continucd Definition FIG. Definition FlG.

N05. N05 Definitions N054 N05, Definitions 30 55A Second gland of P u ng 52 6 Pilot pressure chamber in cylindrical Piston wlicreon the Secondary bore 18 of valve unit i. rormt-ii Lil the Consumer p feefiback l5 8 springloadcd end of spool valve 16. its at the same time forming the throttle other cnd being li d by pressure opening between the primary and mmng five 20 Secondary l bores for 53 6 and 12 Valve chamber above valve cone 22 in colnsume pressure feedback to the pressure limmng valve 20; in Va um continuous flow connection with 3l 5'5A Shank of piston 28 between glands 29 mum Channel 50 via circular bore 54 I and auxiliary bore 55.

32 cylmdncfil bore m 54 6 and 12 Circular bore connecting chamber 53 9 respecti vely, wherein piston 28 is to auxiliary bore 33 5 5A the Stroke of 55 6 and 12 Auxiliary bore connecting bore 54 to p g 28 g return channel 50. v

34 5.5A Pressure-influencing cartridge spring 5 56 4 and 6 Mdmlgldnd-o-f spec valve m acting on piston 28 determining the posmo-n of sp-ool live 10 consmm pressure drop in the closing the primary pilot bores 61 and 62 and interrupting the connection consumer pressure feedback. b h b 49 I) 35 5,5A Adjusting pin for setting the bias stwwn C er P a C pressure of spring 34 to the desired 57 4 I ufnsumer g fi I pressure drop. and 6 First gland of spoo valve It). in neutral 36 55A Lock nut for securing adjustment pin of 5,900] valve mwn'upimg the connedctipn b;twege)n(consun)icr port 7 an c am er return v 37 1 fsfigz g g gg when 58 4 and 6 Second gland of spool valve [0; in

the spool valves 10 are in neutral P PP of 10 position; also producing a leakage loss lmcn'uptmg l fi i b gg during 0 eration, which loss is consumer F an C indepenCi ent of pressure variations; (mmmli d f a good f i i f the 59 4 and 6 Chamber around spool valve l0 in vaive Cartridges 3 and 9 and f continuous flow connection with maintaining a constant pressure l'elllm Chflnncl $66110" 5011v diff b tw pump pressure d 60 4 and 6 Chamber around spool valve l0. in consumer pressure feedback set via continuous flow connection with valve cartridges 8,9. return channel section 506.

38 7 Leak throttle passage axially disposed 3O 61 4,58 and 6 First primary pilot bore ending in bore in piston 37 serving for passing l5 of control valve unit 2, upon hydraulic fluid to the spring-loaded displacement of valve l0 in downward end of piston 37; diameter and length direction (as in FIG. 4) in flow of said bore determines the constant connection with consumer port 7; in leakage loss. neutral position and upon 39 7 and l l Gland of piston 37 for sealing chamber displacement in upward direction of 79a from 79b. valve 10 the mouth of pilot bore 6| is 40 7 and l l Gland of piston 37, forming with blocked by gland 56.

cylindrical bore and leak bore 80 62 4 and 6 Second primary pilot bore ending in 3 throttle p f bore l5 of control valve unit 2, upon 41 7 and ll Cylindrical bore wherein piston 37 is displacement f vaive m in upward Slldabltf dlsplac?abledirection in flow connection with 42 7 and l l Leak piston spring acting on piston 37 consume- PO" in neutral position and l'espollslble fol collstam 40 and upon displacement in downward pressure difference determining the direction of Valve 10 (85 FIG 4) the g leakage loss through passage mouth of pilot bore 62 is blocked by 43 7 and I l screw plugs for plugging the bore 63 4.5 and 6 l ii's t ai i iliary pilotbore at right angles 44 8 and 13 Throttle screw for ad ustmentof the to pilot bore 61 leading to valve throttle passage of the cylindrical cartridge 8 i to adjust the 45 64 4,5 and 6 Second auiiiliary pilot bore at right buildup and pressure drop time at the angles m pilot bore 62 leading to spring-loaded end of spool valve l6.

45 7 8 l2 l3 l4 Screw to revent in ress of dirt valve cartridge p g 6S 5 Primary chamber around housing 46 6 chamger Hound li s i m valve cartridge 8 (or 9). intersected by 3221:3324 0w Connec on I and in continuous flow connection 47 6 Return chamber around piston 16 in 50 66 5 2.": y fg g 1 continuous flow Connection with cai tri d g e t; r i iii cz ii ti ri u o iis i'low return ort Si 48 4,5,6 Pump c hannel running through the f o th chamber 65 at the entire device in continuous flow same time intersecting cylindrical bore connection via chamber 46 with pump 32 harem Piston 28 Slidabl) port displaceable.

49 4 and 6 Chamber around each spool valve 10 67 5 Chamber formed P' the shank of control valve units 2 intersecting of Plsmn and i P) glands 29 pump channel 4 and 30 of piston 28 in cylindrical bore 50a 4.5 and 6 First return channel section corresponding with consumer ports 7 68 5 Second cartridge cross bore in valve of control valve units 2. 8 (or 9). being flow 50b 6 Third return channel section in connecllon with groove retaining plate 3 for connecting return 69 5 9 '9" Valve 8 (of channel section 50a with return g gg p g e g Wllh channel section 50:. P Ol 35 We 35 We 50c 4,5 and 6 Second return channel section 6911 5 Auxiliary cartridge bore Connecting corresponding with consumer ports 6 groove 69 with bore 32 at spnng of control valve units 2 and in biased side of piston 28. continuous flow connection with 70 4.5,6,7.8.l0.5B First secondary pilot bore connected return chamber 47. 5 to groove 69 (or 169) of valve 5| 6 Pressure chamber formed in cartridge 8.

cylindrical bore 18 of valve unit I; 71 4,5679 Second secondary pilot bore,

pump pressure is transmitted via bores 17 into pressure chamber 5|.

connected to groove 69 (or 169) of valve cartridge 9.

FIG. Nos.

Definitions 6.7.9,),1 l.l2,l3.First leak bore. con'n'ecfing bores 77 7andll 7- and ll 7.l2,l3.l4

Auxiliary bore, parallel to auxiliary bore 72b; in flow connection with auxiliary bore 78 to leak piston 37. Auxiliary bore wherein pilot bore 70 ends, parallel to auxiliary bore 72a; also in flow connection with bore 70. Auxiliary bore on bore 72b; leading to the cylindrical space 74.

Throttle bore limited by throttle screw 44.

Continuation of auxiliary bore 73. Cross bore of auxiliary bore 75 leading to pilot pressure chamber 52. Auxiliary bore which communicates pilot bore 71 with auxiliary bgre LS.

and 72a with chamber 790 at one end of leak piston 37.

First leak. chamber limited by leak piston 37 and screw plug 43; connecting leak bore 78 via passage 38 in piston 37 with chamber 791: at the spring-loaded end of piston 37. Second leak chamber at springloaded side of piston 37.

Second leak bore ending in the chamber 791: at the spring-loaded end of piston 37. the gland 40 of said piston forming a throttle opening between said chamber and said bore. Auxiliary leak bore connecting bore 80 with circular bore 54 so that via bore 54 and bore 55 there is a flow connection between bore 80 and return channel section 50a.

Tie rods with which the components l.

2 and 3 are held together.

Nuts on tie rods 81.

Control mechanism for displacing spool valves 10 of control valve units 2.

Operatinglever of control mechanism 83 position through the action of spring Spring guides. also acting as stroke limitation for the displacement to be made by control piston 10. Auxiliary bore connecting chamber 59 (return channel 50a) with the interior of the control mechanism 83 and permitting change of the hydraulic fluid volume in control mechanism 83 as valve 10 is displaced.

Auxiliary bore connecting return channel 50c with the interior of the spring cap 87 and permitting change of hydraulic fluid volume therein as valve l is displaced.

Cone of valve cartridge I80. Cylindrical bore in valve cartridge [80.

Pressure-influencing cartridge spring of valve cartridge [80.

Adjust screw for setting the bias pressure of spring 134.

Primary chamber.

Cartridge cross bore.

Groove.

Variant of pressure-influencing valve cartridge 8 or 9.

Valve seat of valve cartridge I80. Bore in valve seat 18].

DESCRlPTlON OF THE PREFERRED EMBODIMENT For a better understanding of the whole complex of consumer pressure feedback and production of an arbitrarily set constant difference between pump pressure and consumer pressure, the valve cartridges 8 and 9 and the leak piston are described before the whole device is described.

A. Valve cartridges 8 and 9.

FIG. 5A shows an enlargement of the cross section of a valve cartridge 8. it is clear that the construction of a valve cartridge 9 is fully identical, so that a description of a valve cartridge 8 will suffice.

As shown in FIG. 5A, a valve cartridge 8 comprises a metal housing with hexagonal faces, a screw thread and a shoulder. Such a cartridge may be screwed into the housing of the control valve units 2 (a,b,c, In the drawn embodiment, the housing of such a valve cartridge is provided with an axially disposed cylindrical bore 32. In said cylindrical bore 32 the pressureinfluencing piston 28 has been slidably mounted. Piston 28 comprises a shank 31 and two glands 29 and 30. The stroke of pressure-influencingpiston 28 is limited in one direction by a stop collar 33.

The cartridge is provided with a first cross bore 66,

iliary bore 69a is formed from said groove 69, leading at an angle to cylindrical bore 32.

The pressure-influencing piston 28 is pressed against stop collar 33 by means of the spring force of a cartridge spring 34, and forming a chamber 67 between the glands 29 and 30 in cylindrical bore 32, said chamber being in communication, via first cross bore 66, with a primary chamber 65 which is formed around cartridge 8, after screwing it into the housing of a control valve unit 2 (a,b,c, 1

The chamber 67 between the glands 29 and 30 is, via first cross bore 66 and chamber 65, in continuous flow connection with the end of pressure-influence piston 28 at gland 29, while gland 30 closes off communication between the chamber 67 and cross bore 68.

The bias force of cartridge spring 34 is set, by means of adjusting pin 35, whichis screwably disposed in the cylindrical bore 32 and secured against loosening by vibration during operation byv lock nut 36.

The valve cartridge 8 is so disposed in the housing of control valve unit 2 (a,b,c, that bore retaining the valve cartridge intersectsa pilot auxiliary bore 63. Said bore 63 is in continuous flow connection with the primary pilot bore 61, which, as shown in FIG. 4, ends in cylindrical control valve bore 15 for the control spool valve 10. i

When new control spool valve 10 (FlG. 4) is moved downwards, there is established a connection between first consumer port 7 and bore 6l.'The pressure prevailing in first consumer port 7 is transmitted via bores 61, 63 and chamber 65 to pressure-influencing piston 28 at gland 29. At the sametime the consumer pressure is transmitted into chamber 67, but as the glands 29 and 30 are fully identical, the pressure prevailing in chamber 67 has no influence on the displacement of piston 28. A

As soon as the Consumer pressure, in chamber 67 against gland 29 at the end of piston 28, overcomes the bias force of spring 34, the piston 28 is moved against the action of spring 34, thus producing a communication between chamber 67 and cross bore 68. Consequently, there flows, via cross bore 68 and groove 69 and auxiliary bore 69a, fluid into the cylindrical bore 32 at the spring-loaded side of piston 28.

Consequently, in addition to the biasing force of spring 34 at this end of piston 28, there also prevails hydraulic pressure. The displacement of piston 28 therefore only continues until the secondary pressure acting over the cross-sectional area of the spring-loaded gland 30, together with the bias force of the spring 34, is equal to the primary pressure from the consumer port 7 acting on the gland 29 of piston 28.

Upon increasing consumer pressure, piston 28 is so far moved against the action of spring 34 until the pressure drop again has attained a value corresponding to the bias force of spring 34. Now it is clear that an increased bias force of spring 34 produces a greater (and a reduction of the bias force, a lower) pressure drop but that a once arbitrarily set pressure drop remains constant, however great the consumer pressure variations may be. 7

Upon decreasing primary consumer pressure the piston 28, as shown in FIG. A, would act as a non-return valve, for then the pressure at the gland 30 of the piston 28 would be decreased, after which, without suitable provisions, displacement of piston 28 would take place, as a result of which the communication between bore 68 and chamber 67 would be shut off. This would mean that the difference between pump pressure and consumer pressure would increase and, consequently, more hydraulic medium would pass to the consumer.

To avoid this, a leak piston 37 has been disposed in the pressure regulating valve unit 1, causing a constant leakage loss, as a result of which increases of the secondary consumer pressure at the spring-loaded end of pressure-influencing piston 28 are continuously levelled in conformity with the varying primary consumer pressure.

The fact that the valve cartridge 8 can also function as a non-return valve is of great advantage to the control device, for now two control valve units 2 can be displaced simultaneously, as the load pressure of the heaviest loaded consumer keeps the valve cartridge 8 closed against the less heavier loaded consumer in the above described manner and, consequently, only the load pressure of the heaviest loaded consumer is fed back. Upon simultaneous operation of various control valve units 2, the pump pressure will therefore adjust itself under all circumstances to the highest consumer pressure, as a result of which all consumers can be operated and controlled.

A variant 180 of the described pressure-influencing valve cartridges 8 and 9 is represented by FIG. 5B. This variant is simpler and because of that cheaper in production. However, the accuracy of adjustment is somewhat less good, but in practice good enough for a number of applications.

The pressure-influencing piston 28 has been replaced by a cone 128, which closes a bore 182 in a valve seat 181. The bore 182 is in flow connection with primary pilot bore 61 (respectively 62). The cone 128 is loaded by a spring 134 of which the spring force is adjustable by an adjust screw 135.

Whenever a spool valve 10 (FIG. 4) is moved downwards, a flow connection is established between consumer port 7 and primary pilot bore 61. The pressure prevailing in consumer port 7 is via chamber 165 and the bore 182 transmitted to the cone 128.

As soon as the primary consumer pressure on cone 128 overcomes the bias force of spring 134, the 'cone 128 is moved from seat 181, this producing a flow communication between chamber 165 and cross bore 168. Consequently, fluid flows via cross bore 168 around groove 169 into the secondary pilot bore 70.

Since the diameter of cone 128 is smaller than the diameter of bore 132, the pressure available in bore prevails within bore 132. Consequently, in addition to the biasing force of spring 134 at the cone 128, this cone 128 is loaded with secondary consumer pressure feedback as well.

So the cone 128 is closing the bore 182 of seat 181 again at the moment that the primary consumer pressure feedback prevailing in bore 182 is equal to the sum of secondary consumer pressure feedback prevailing in bore 70 and the bias force of spring 34. The working principle in fact is that of a sequence valve.

It is clear, that also a valve cartridge of this type functions as a non-return valve as well as that here also the pressure drop between the primary pilot bore 61 and secondary pilot bore 70 is determined by the adjustable biasing force of spring 134. Furthermore, it is obvious that the cone 128 could be'replaced by a ball.

B. Leak Piston 37.

As shown above, the production of a leakage loss is a necessity for the correct functioning of the valve cartridges 8 and 9, it being required, however, to keep the leakage loss produced within preestablished limits and independent of pressure variations. Such a leakage loss can be caused by a leak position 37, as shown in the pressure requlating valve unit 1 shown in FIGS. 7 and 11.

As shown in FIG. 7, pressure regulating valve unit 1 is provided with a cylindrical bore 41, wherein a leak piston 37 is slidingly displacable. Piston 37 is provided with glands 39 and 40 of which gland 39 bounds and seals a first leak chamber 79a in cylindrical bore 41 and gland 40 bounds and seals a second leak chamber 79b. Both chambers 79a and 79b are in continuous flow connection with each other via a leak throttle passage 38 axially disposed in piston 37. In chamber 79b furthermore there is a spring 42 acting on piston 37. Cylindrical bore 41 is sealed at both ends by a screw plug 43.

The bore 41 is intersected in chamber 790 by a leak bore 78, which in a manner as explained hereunder is in continuous flow connection with the pilot pressure chamber 52 (FIG. 6) at the end of spool valve 16 loaded by the light control spring 19 of pressure differential valve unit 1. The same bore 78 furthermore is in continuous flow connection with groove 69 around the valve cartridges 8 and 9 (FIG. 5).

Chamber 79b of cylindrical bore 41 is furthermore in continuous flow connection with a second leak bore 80, which via auxiliary leak bore a (FIGS. 7,12) is in continuous flow connection with circular bore 54 of the pressure limiting valve 20. The mouth of leak bore 80 and chamber 7912, together with gland 40, form a throttle opening.

As soon as one control spool valve 10 of one of the control valve units 2 (a,b,c, is displaced, fluid will flow in the earlier described manner into groove 69 around valve cartridge 8 (or 9) and, since said groove is in connection with the bore 78, the pressure in chamber 79a will increase, as a result of which the leak piston 37 will be displaced in a direction opposite to the action of spring 42, and gland 40 will reduce the throttle opening between chamber 79b and bore 80.

At the same time fluid also passes via throttle passage 38 from chamber 79a into chamber 79b, which fluid can only pass the throttle opening formed by gland 40 with bore 41 and 80 with a pressure drop. On leak piston 37 are thereby acting two forces, viz. at gland 39 the pressure in chamber 790 and at gland 40 the pressure of spring 42, as well as the pressure prevailing downstream of the throttle point between bore 41 and bore 80. The piston consequently, will be displaced and adopt an equilibrium position, wherein both forces are in equilibrium and, consequently, the pressure drop at said throttle opening, together with the force exerted by spring 42, is equal to the pressure in chamber 79a.

The pressure difference upstream and downstream of piston 37 is determined by the spring force of spring 42 and, this being to all intents and purposes constant, also the pressure difference is constant. The volume passed through throttle passage 38 per unit of time is then determined by the difference between the pressures in chambers 79a and 79b, and by the diameter and the length of throttle passage 38 and, as all three factors are constant, also the volume passed or the leakage loss produced is constant under all circumstances.

As a result of the action of leak piston 37, a valve cartridge 8 or 9, upon decrease of the consumer pressure, will not function as a non-return valve, since the earlier consumer pressure feedback, through the action of the piston 37, decreases simultaneously with the pressure drop of the actual consumer pressure. As always, very small volumes of fluid are displaced, load pressure changes are dealt with without delay, and a leakage loss of approximately 20 cc per minute, at a spring force corresponding to 2 kg/cm of oil pressure on spring 42, is sufficient in practice.

When spool valves of control valve units 2 (a,b,c, are in the neutral position, no further supply of fluid feedback takes place. As a result of the leakage produced in piston 37, the pressure in chamber 79a is diminished and as chamber 79a is in flow connection with pilot pressure chamber 52 at the spring-loaded end of spool valve 16 by means of bores 78, 72a, 70, 72b, 73, 74, 75, and 76, the latter is relieved at its spring-loaded end.

C. Embodiment of an entire control device.

According to FIG. 1, the control device with pressure-compensated volume control is composed of a single pressure regulating valve unit 1 and three control valve units 2a, 2b and 2c. Said units are effectively bolted together by means of a retaining plate 3 and a plurality of tie rods 81 to create a single device.

The pressure regulating valve unit 1 is provided with a pump port 4 and a return port 5 which serve respectively for connecting the device to a pump for supplying hydraulic fluid and to a reservoir for discharging returning fluid from consumers connected to the device, as well as for the discharge of that part of the pump yield which is not passed for direct supply of the system. Each of the control valve units 2 (a,b,c, is provided with two consumer ports 6 and 7 serving for connecting a double-acting consumer. It is clear that if the downstream consumer need only be operated in one direction, the corresponding control valve unit 2 (a,b,c, need only be provided with one of the consumer ports 6 or 7.

The pump port 4, as shown in FIG. 6, ends in a pump chamber 46 wherein also ends a centrally disposed pump channel 48. The channel 48 traverses the entire device and intersects in each control valve unit 2 (a,b,c, a cylindrical control valve bore 15 axially disposed in the housing of each control valve unit 2 (017,0, A chamber 49 is disposed each time where the pump channel 48 crosses such a bore 15. The pump channel 48 is bounded and shut off by retaining plate 3.

The return port 5 ends in a return chamber 47 which again is in continuous flow connection with a return channel section 500 of a return channel 50, which also traverses the entire device. Via a return channel section 50b in the retaining plate 3, return channel section 50c is in continuous flow connection with a return channel section 50a. Channel section 50a also traverses the entire device. Both return channel sections 50a and 50c intersect, as is the case with pump channel 48, the control valve bores 15 as well. Where return channel section 50a crosses bore 15 there is disposed a chamber 59. Where the return channel section 50c crosses bore 15 there is also disposed a chamber 60.

As shown in FIGS. 4 and 6, there is disposed in bore 15 of each control valve unit 2 (a,b,c, a control spool valve 10 which is slidingly displaceable. which in the neutral position drawn in FIG. 6, closes the connection between pump channel 48 and consumer port 7 and between pump channel 48 and consumer port 6 by the main gland 56 disposed on spool valve 10.

In the same way the spool valves 10 of each control valve unit 2 (a,b,c. shut off, through its gland 57, the connection, between return channel section 50aand consumer port 7, as well as through its gland 58, the connection between return channel section 5900 and consumer port 6. A consumer connected to the consumer ports 6 and 7, in the neutral position, is therefore neither in flow connection with the pump nor with the reservoir. In practice it may occur that one or even both sides of a consumer in the neutral position of control valve unit 2 has to remain in flow connection with the reservoir or with the pump. It is clear that for such cases the glands 56, 57 and 58 will have a different form.

It is also shown in FIGS. 4 and 6 that in each control valve unit 2 (a,b,c, two primary pilot bores 61 and 62 end in control valve bore 15 and that the mouths of said pilot bores 61 and 62, in the neutral position as drawn, are also closed off by the main gland 56 of spool valve 10.

The displacement of spool valve 10 in bore 15 is produced by displacement of a operating lever 84, as shown in FIG. 4. Operating lever 84 is screwed into a pinion 86, whose teeth engage the teeth of the toothed rack 85 disposed on spool valve 10. Displacement of operating lever 84 in the upward direction produces a displacement of spool valve 10 in the downward direction, while displacement of operating lever 84 in the downward direction produces a displacement of spool valve 10 in the upward direction.

As shown in FIG. 4, each control valve unit 2 (a,b,c, is provided at the end opposite to operating lever 84 with a spring mechanism which ensure that spool valve 10, after releasing operating lever 84, automatically returns to its neutral position. Each spring mechanism comprises a centering spring 88 and two spring guides 89 and is enclosed in a space bounded by spring cap 87. Spring guides 89 ensure a good guiding of spring 88, as well as limiting the stroke of spool valve 10.

It will be noted that the embodiment described here allows many variations, which make no difference, however, to the function of the invention as long as spool valve can be moved upwards and downwards by hand, hydraulically, mechanically or other means.

It can be easily seen from FIG. 4, that, upon displacement of spool valve 10 in upwards direction, first the mouth of pilot bore 62 comes in flow connection with consumer port 6, so that fluid from consumer port 6 passes into pilot bore 62, so that the consumer pressure (or load pressure) also prevails in pilot bore 62.

It is also clear that further movement of spool valve 10 in upwards direction then opens a connection between pump channel 48 and consumer port 6 and that, consequently, fluid flows from pump channel 48 via consumer port 6 to the consumer.

On the other hand, upon displacement of spool valve 10 in downwards direction as shown in FIG. 4, there will first be effected a flow connection between consumer port 7 and pilot bore 61 and only upon further movement of spool valve 10 in downward direction will there be produced a flow connection between pump channel 48 and consumer port 7. Of decisive importance for the entire functioning of the device is the fact that the mouths of the pilot bores 61 and 62 in valve bore are shut off by gland 56 in the neutral position of spool valve 10, while upon movement of spool valve 10 in one of the operative positions, gland 56 only ceases to occlude that mouth which corresponds with the consumer'port actually brought in communication with pump channel 48. It can also be seen in FIGS. 4 and 6 that upon downward movement of spool valve 10 (see FIG. 6, control valve unit 2c), gland 58 releases a connection between consumer port 6 and return channel section 50c. In that case the consumer is loaded at one side via port 7 as stated above and via port 6 relieved at the other side. In the same way upon upwards movement of spool valve 10 the consumer is loaded at one side via port 6 and relieved at the other side via port 7.

In the above manner it is therefore possible arbitrarily to cause a consumer connected to a control valve unit 2 (a,b,c, to perform a movement, to have said movement stopped and to reverse same. The volume passed to a consumer is determined by the control orifice between the pump channel 48 and the currently connected consumer port 6 or 7. For example, the control valve unit 2c of FIG. 6 is drawn in a displaced condition. Here the control orifice is formed because gland 56, upon movement in downwards direction of spool valve 10, opens an orifice between chamber 49, in flow connection with pump channel 48, and that part of valve bore 15 which is in flow connection with consumer port 7, thus realizing a connection between pump channel 48 and consumer port 7.

Gland 56 is provided with a cone 11, also called a control land. It is clear that with a continued displacement of spool valve 10, as a result of the presence of 7 control land 11, the control orifice becomes increasingly larger. The volume of fluid passed from pump channel 48 to consumer port 7 is determined by the size of said control orifice, as well as by the difference between pressures upstream and downstream of said control orifice. By keeping said pressure difference 5 constant, the volume passed to the consumer is therefore only dependent on the size of the control orifices and consequently, the volume is exclusively determined by the displacement of spool valve 10.

Obviously, upon displacement of spool valve 10 in upwards direction, the gland 56 with control land 12 can effectuate a similar control orifice between pump channel 48 and consumer port 6. The form of the control lands 11 and 12 determines the control orifice. When these control lands have been disposed at a small angle, the control orifice is small and therefore also the throughflow at full displacement of spool valve 10. The greater this angle, the greater the control orifice at full displacement of spool valve 10 and, consequently, also the maximum volume of fluid passed is greater. Furthermore it is clear that in addition to the form of the control lands 11 and 12 on gland 56, also the stroke of control piston 10 determines the volume passed to the consumer and that by limiting said control stroke also the maximum volume of fluid passed is limited.

FIG. 4 shows that the pilot bore 61 is intersected by an auxiliary pilot bore 63 and the pilot load pressure bore 62 by an auxiliary pilot bore 64. FIG. 5 shows that bore 63 opens into the chamber around valve cartridge 8 and that bore 64 opens into the chamber around valve cartridge 9. Upon displacement of spool valve 10 in downwards direction, bore 63 receives, via pilot bore 61, fluid at consumer pressure from consumer port 7. Upon displacement fo spool valve 10 in upwards direction, bore 64 similarly receives fluid at consumer pressure from consumer port 6.

It has already been described that the pressureinfluencing piston 28 of valve cartridge 8 or 9 is adapted to effect a flow connection between the chamber 67 and annular groove 69, whereby, however, a pressure drop is produced that is determined by the bias force of spring 34. Since, as already said, bore 63 is in connection with chamber 65 of valve cartridge 8, and said chamber 65 being in communication with chamber 67 via cross bore 66, fluid will flow from consumer port 7 in annular groove 69 of cartridge 8 upon displacement of spool valve 10 in downwards direction. Upon displacement of spool valve 10 in upwards direction, fluid will therefore flow from consumer port 6 into an identical annular groove 69 of valve cartridge 9.

The annular groove 69 around valve cartridge 8 is in continuous flow connection with a secondary pilot bore 70, while the same annular groove 69 around valve cartridge 9 is in continuous flow connection with a secondary pilot bore 71. As shown in FIG. 6, both secondary pilot bores intersect all control valve units 2 (a,b,c, Within the housing of pressure regulating valve unit 1, bore 71, as indicated in FIGS. 6 and 7, opens into auxiliary bore 77 which is in continuous flow connection with first leak bore 78. The bore 70 intersects, within the housing of pressure regulating valve unit 1, bores 72a and 72b. Bore 72a is in continuous flow connection with bore 78, so that chamber 79a, at the end of leak piston 37 opposite spring 42, is in continuous flow connection with both pilot bores 70 and 71.

Auxiliary bore 72b as shown in FIGS. 8 and 10, is in continuous flow connection with bore 73. Bore 73 opens into a throttle bore 74 and continuing thereafter 

1. In a hydraulic device for the control and load-independent regulation of hydraulic consumers of a hydraulic medium, said device comprising: A. two consumer ports; B. a pump channel and a return channel connected to said consumer ports; C. a control spool valve through which each said consumer port can be selectively connected with said pump channel or said return channel; D. a pressure-regulating valve unit, for maintaining a constant pressure difference between said pump channel and said consumer ports connected thereto, comprising a pressure-regulating spool valve forming a regulating throttle orifice between said pump channel and said return channel as a result of:
 1. pump pressure acting on one end of said pressure-regulating spool valve and
 2. the sum of consumer pressure, propagated from said consumer ports through pilot bores, plus a regulating valve spring acting on the other end of said spool valve; and E. supply and discharge means for said hydraulic medium towards and away from said spool valve, the improvement comprising a pressure-influencing valve cartridge which interrupts at least one of said pilot bores.
 2. a return port, which is connected to a return channel, for discharging said hydraulic medium to a reservoir in said hydraulically driven installation;
 2. the sum of consumer pressure, propagated from said consumer ports through pilot bores, plus a regulating valve spring acting on the other end of said spool valve; and E. supply and discharge means for said hydraulic medium towards and away from said spool valve, the improvement comprising a pressure-influencing valve cartridge which interrupts at least one of said pilot bores.
 2. The improvement of claim 1 wherein said pressure-influencing valve cartridge comprises a pressure-influencing cartridge spring and a pressure-influencing piston which, by variation of the axial displacement thereof, forms a pilot throttle orifice in said at least one pilot bore, whereBy one end of said piston is under the influence of the pressure upstream of said pilot-throttle orifice and its other end is under the influence of the pressure downstream of said pilot-throttle orifice and of said cartridge spring.
 2. a leak piston spring which acts within said second leak chamber against the downstream end of said piston, and
 2. a control spool valve through which each said consumer port can be selectively connected with a pump channel or a return channel,
 2. supply and discharge means for the hydraulic medium from and towards said pressure regulating spool valve, and
 2. a control spool valve through which each said consumer port can be selectively connected with a pump channel and a primary pilot bore or with a return channel,
 2. two consumer ports,
 2. first and second consumer ports which are selectively connected with said pump channel or with said return channel and with said one hydraulic consumer,
 3. a primary pilot bore which provides flow connection with one of said consumer ports and transmits primary consumer pressure therefrom, and
 3. a pressure regulating spool valve which is loaded at one end with said pump pressure and at its other end with pressure from a regulating valve spring plus secondary consumer pressure within a pilot pressure chamber, said secondary consumer pressure being fed back thereto via secondary pilot bores, and
 3. a pressure-influencing valve cartridge which selectively interrupts the through-connection of said primary pilot bore with a secondary pilot bore and comprises a pressure-influencing piston which, by variation of its axial displacement forms a pilot throttle orifice in said pilot bores, whereby one end of said pressure-influencing piston is under the influence of the pressure upstream of said pilot-throttle orifice and its other end is under the influence of the pressure downstream of said pilot-throttle orifice and of a pressure-influencing cartridge spring; B. a pressure regulating valve unit for maintaining a constant pressure difference between said pump channel and said consumer ports connected with said pump channel, said pressure regulating valve unit comprising:
 3. a leak piston which interrupts leak bores branching from said pilot bores downstream of said pilot-throttle orifice and leading to said return channel, said leak piston forming a first leak throttle orifice in said leak bore for producing a constant leakage, whereby one end of said leak piston is in a first leak chamber and under the influence of the pressure in said pilot bores and its other end is in a second leak chamber and under the influence of the pressure downstream of a leak throttle passage through said leak piston but upstream of a second leak throttle orifice formed between said second leak chamber and said leak bores, as well as under the pressure of a leak piston spring.
 3. primary pilot bores which are selectively through-connected with one of the consumer ports of each said at least one control valve unit by a main gland of the corresponding control spool valve, and
 3. a leak-throttle passage, axially disposed in said leak piston, which provides the throughflow of the hydraulic fluid between said first leak chamber, being in flow connection with said pilot bores at one end, and said second leak chamber, being in flow connection with said return channel at the spring-loaded downstream end of said leak piston.
 3. The improvement of claim 2 which further comprises a leak piston, which interrupts first and second leak bores branching from said at least one pilot bore downstream from said pilot-throttle orifice and leading to said return channel, said leak piston forming in said leak bores a first leak throttle orifice for producing a constant leakage, whereby one end of said leak piston is in a first leak chamber and under the influence of the pressure in said at least one pilot bore and its other end is in a second leak chamber and under the influence of the pressure downstream of said first leak throttle orifice but upstream of a second leak throttle orifice formed between said second leak chamber and said second leak bore, as well as under the pressure of a leak piston spring.
 4. a pressure limiting valve, which separates said pilot pressure chamber from a valve chamber, for selectively limiting the maximum permissible system pressure by selectively passing said hydraulic medium from said pilot pressure chamber to said valve chamber which is connected to said return channel; and B. a control valve unit for directing said hydralic medium to and from one of said hydraulic consumers, comprising:
 4. The improvement of claim 3 which further comprises a throttle screw which adjustably interrupts said at least one pilot bore for adjustment of the throttle passage therewithin in order to adjust the pressure build-up and pressure drop time at said spring-loaded other end of said pressure-regulating spool valve.
 4. at least one pressure-influencing valve cartridge which interrupts the connection of said primary pilot bores with secondary pilot bores by forming a pilot-throttle orifice therein; B. a pressure regulating valve unit for discharge of pump pressure in said neutral position and for producing a constant pressure difference in said flow positions between said pump channel and the consumer ports connected therewith.
 4. a pressure-influencing valve cartridge which is connected to and interrupts said primary pilot bore and is connected to said secondary pilot bores.
 5. A device for the control and load-independent regulation of a hydraulic medium supplied to hydraulic consumers of hydraulically driven installations, comprising: A. a pressure regulating valve unit for discharging pump pressure and for producing a constant pressure difference required for load-independent volume control of said hydraulic medium, comprising:
 6. The device of claim 5 wherein said pressure-influencing valve cartridge comprises a pressure-influencing piston and a cartridge spring which loads the end of said piston in flow contact with said secondary pilot bores.
 7. The device of claim 6 wherein said pressure-influencing valve cartridge further comprises a stop means for said pressure-influencing piston which stops movement of said piston and shuts off communication between said primary pilot bore and said secondary pilot bore when said secondary consumeR pressure in said secondary pilot bores plus the pressure of said cartridge spring exceeds said primary consumer pressure in said primary pilot bore, whereby said pressure-influencing valve cartridge functions as a non-return valve.
 8. The device of claim 7 wherein said pressure regulating valve unit further comprises a leak piston, which is connected to said secondary pilot bores and to said return channel, for discharging said pump pressure when said spool valve is in neutral position and for producing a pressure-independent leakage loss during operation, whereby increases of said secondary consumer pressure are continuously levelled in conformity with variations of said primary consumer pressure so that said valve cartridge is responsive to decreases in said primary consumer pressure.
 9. The device of claim 8 wherein said control valve unit is connected by means of said pump channel and said return channel to additional control valve units, each connected to one of said hydraulic consumers, whereby at least two of said control valve units can be displaced simultaneously because the highest consumer pressure from the heaviest loaded of said consumers maintains said valve cartridge connected to the lesser loaded of said consumers in closed position, whereby said pump pressure adjusts itself to said highest consumer pressure so that all of said consumers can be operated and controlled.
 10. A control device for the control and load-independent regulation of hydraulic consumers of hydraulically driven installations, comprising: A. at least one control valve unit, each comprising:
 11. The control device according to claim 10 wherein said at least one pressure influencing valve cartridge is accommodated within a cylindrical bore in said control valve unit and further comprises: A. a primary chamber which is formed between said valve cartridge and the walls of said cylindrical bore and is connected with said primary pilot bore and with said one end of said pressure-influencing piston; B. an axially disposed bore; C. a first cartridge cross bore, radially disposed in said cartridge, which connects said primary chamber with said axially disposed bore; and D. a second cartridge cross bore, radially disposed in said cartridge, which provides fluid connection between said axially disposed bore and said secondary pilot bore, said connection being selectively interruptible by said piston to form said pilot-throttle orifice.
 12. The control device of claim 11 wherein said at least one pressure-influencing valve cartridge additionally comprises: A. a circumferential groove forming an annular chamber which is connected with said secondary pilot bore; and B. cross bores which are disposed at an angle to and connect said annular chamber with said axially disposed bore at said other end of said pressure-influencing piston.
 13. The control device of claim 12, wherein said pressure-influencing piston is slidable in said axially disposed bore, said pressure-influencing piston comprising a shank having at each end a gland, said glands bounding a chamber in said axially disposed bore around said shank, one of said glands forming said pilot-throttle orifice, upon displacement of said pressure-influencing piston against the action of said cartridge spring, between said chamber and said second cartridge cross bore, while said chamber is in continuous flow connection via said first cartridge cross bore with said primary chamber and with said one end of said pressure-influencing piston.
 14. A control device for the control and load-independent regulation of hydraulic consumers of a hydraulically driven installation, comprising: A. at least one control valve unit adapted for setting in a neutral position or in either of two flow positions, each comprisng:
 15. The control device of claim 14 wherein each said at least one valve cartridge comprises a combination of a cone, loaded by a cartridge spring, and a valve seat with a valve bore, whereby one end of said cone is under the influence of the pressure upstream of said pilot-throttle orifice and its other end is under the influence of the pressure downstream of said pilot-throttle orifice and of said cartridge spring.
 16. The control device of claim 14 wherein each said at least one valve cartridge comprises a combination of a ball, loaded by a cartridge spring, and a valve seat with a valve bore, whereby one end of said ball is under the influence of the pressure upstream of said pilot-throttle orifice and its other end is under the influence of the pressure downstream of said pilot-throttle orifice and of said cartridge spring.
 17. The control device of claim 14 wherein each said at least one valve cartridge comprises a combination of a piston, loaded by a cartridge spring, and a valve seat with a valve bore, whereby one end of said piston is under the influence of the pressure upstream of said pilot-throttle orifice and its other end is under the influenCe of the pressure downstream of said pilot-throttle orifice and of said cartridge spring.
 18. The control device of claim 14 wherein said at least one valve cartridge comprises: A. a piston, having a downstream end connected with said secondary pilot bores and an upstream end in contact with consumer pressure propagated through said primary pilot bores; and B. a resilient biasing means which exerts a selected bias force upon said downstream end.
 19. The control device of claim 18 wherein said resilient biasing means is a cartridge spring and said bias force is selected so that, upon increase of the sum of the pressure in said secondary pilot bores and said bias force to a pressure equal to or higher than the pressure in said primary pilot bores, the connection between the corresponding consumer port and said pressure regulating valve unit is selectively interrupted.
 20. The control device of claim 19 wherein said pressure-regulating valve unit comprises a leak piston, which interrupts leak bores branching from said secondary pilot bores downstream of said pilot-throttle orifice and leading to said return channel, for producing a constant leakage loss, independent of hydraulic pressure variations.
 21. The control device of claim 20 wherein said leak piston: A. is slidably disposed in a cylindrical bore and B. is provided with:
 22. The control device of claim 21 wherein said leak piston is connected to more than one said control valve unit and said pressure regulating valve unit comprises a pressure regulating spool valve, which forms a regulating throttle orifice between said pump channel and said return channel, and supply and discharge means for said hydrulic medium from and towards said pressure regulating spool valve.
 23. The control device of claim 22 wherein said pressure regulating valve unit comprises: A. at one end of said pressure regulating spool valve, a pressure chamber; B. in the interior of said pressure regulating spool valve, cross bores for transmitting pump pressure from said supply means to said pressure chamber, C. at the other end of said pressure regulating spool valve, a pilot pressure chamber which is in flow connection with said first leak chamber and said secondary pilot bores whereby feedback consumer pressure is propagated to said pilot pressure chamber; D. a regulating valve spring which acts within said pilot pressure chamber upon said other end of said pressure regulating spool valve, said regulating valve spring being responsible for the constant pressure difference between said pump pressure and said feedback consumer pressure; E. a valve chamber which is in continuous flow connection with said return channel; and F. a pressure limiting valve, which selectively separates and forms one wall of both said pilot pressure chamber and said valve chamber, adapted for limiting maximum system pressure by selectively acting on said feedback consumer pressure to tramsmit said hydraulic medium from said pilot pressure chamber to said valve chamber when said feedback consumer pressure exceeds a selected maximum pressure therefor.
 24. The control device of claim 23 wherein: A. said pump is a controllable yield pump which is provided with an adjusting cylinder for effecting the setting of said pump in accordance with the pressure exerted by the return flOw through said discharge means of hydraulic medium not passed to said consumer; B. an additional discharge means for passing hydraulic medium passed to said consumers from said consumers to the reservoir of said hydraulically driven installation; C. a throttle valve, connected to said adjusting cylinder, which throttles said not-passed hydraulic medium, whereby pressure of said not-passed hydraulic medium causes said adjusting cylinder to adjust delivery of said pump so as to correspond to little more than the volume passed to said consumers so that by adjustment of said pressure-influencing valve cartridges the pump yield corresponds to the fluid volume usefully passed to said consumers.
 25. The control device of claim 23 wherein for the regulation of the pump delivery in accordance with the available motor capacity for driving the pump, a pressure reducing valve is disposed in an intermediate unit mounted between the pressure regulating valve unit and said control valve unit, said pressure reducing valve acting on the combined pilot bore between said valve cartridges and said pressure regulating valve unit, and functioning as a pressure reducing valve with a slide valve mechanism whose pressure reducing piston is similar to the corresponding pressure-influencing piston of said pressure-influencing valve cartridges.
 26. The control device according to claim 25 wherein said pressure reducing piston is loaded with a spring bias force which is directly controlled by the displacement of a piston acting on said force of a single-acting cylinder when the pressure of the pump overcomes the bias of the spring of said cylinder.
 27. The control device according to claim 26 wherein said pressure reducing piston is loaded by the electrically controllable force of an armature of a control solenoid, the electrical signal being given by an electric potentiometer, the resistance of which is changed by the displacement of a piston of a pressure device when the pressure of the pump overcomes tension of the spring of said pressure device. 